So far the casting is great and it seems like all the actors have a solid grasp of the source material. Lan and Moiraine stand out in particular.
I'm only on the second episode so I can't say much more but from the dialogue and portrayal of the Two Rivers village to the climactic battle scene in the first episode I'm pretty sold so far.
Excellent comment, I was just thinking about this while I was watching the show. The casting does a lot of storytelling itself. Even people who haven't read the books should be able to pick up on this after seeing the ruins of skyscrapers in the background.